The regulation of membrane phospholipid synthesis in relation to membrane growth and assembly will be investigated by a combined biochemical and genetical approach in Escherichia coli. Past work has resulted in the selection and characterization of mutants defective in membrane phospholipid synthesis as a consequence of altered sn-glycerol 3-phosphate metabolism. Our work has centered on the sn-glycerol 3-P dehydrogenase encoded by the gpsA gene and the sn-glycerol 3-P acyltransferase encoded by the plsB gene. Recent work using hybrid plasmids contining the plsB gene identified the plsB gene product as an 83,000 dalton peptide. The enzyme has been purified to homogeneity. Future work seeks to define the structure - primary sequence of the plsB gene and the gene product, to study in vitro the synthesis and assembly of the acyltransferase, to determine the phospholipid specificity of its reconstitution its substrate specificity, and its topography within the membrane.